Our interest is in human enzymes involved in ethanol metabolism. The objective of the project was to determine if metabolism of ethanol-generated acetaldehyde had any effect on betaine aldehyde metabolism in rat liver. It has been reported and confirmed that levels of betaine are decreased in rat livers following feeding of rats with ethanol. We recently identified human betaine aldehyde dehydrogenase and found that the enzyme could also metabolize acetaldehyde at low Km value (one fifth that of betaine aldehyde) and at ca. 10% of betaine aldehyde velocity. Rats were fed an ethanol-containing liquid diet, pair fed controls received isocaloric diet without ethanol. After 3-4 weeks the livers were removed and frozen immediately in dry ice-acetone mixture. Aliquots were homogenized in 1N HCl in the presence of internal deuterated standard and after centrifugation chromatographed on BIO-RAD AG-50W-X8 ion exchanger. Betaine aldehyde was eluted with 2.5N HCl and following lyophilization and derivatization with n-butanol was analyzed via FAB-MS, which permitted this compound to be unambiguously identified and quantified.